Occupational Noise Assessment Guidelines

Noise can cause hearing damage that is permanent and disabling, and you may not become aware of the hearing loss until several years have gone by. Long-term exposure to noise in the workplace is also associated with hypertension and other chronic conditions. Ensuring a safe working environment is crucial for the health and well-being of employees. One significant aspect of workplace safety is managing noise levels to prevent hearing loss and other noise-induced health issues.

This article provides guidelines for occupational noise assessment, including measurement techniques, exposure limits, hearing protection, and hearing conservation programs. A-weighted noise levels or dBA is used to predict hearing risk. Decibels (dB) are a scale for measuring noise.

All University employees whose noise exposures equal or exceeds an eight-hour time weighted average (TWA) of 85 decibels are enrolled in a hearing conservation program. When information indicates that any employee’s exposure may equal or exceed an 8-hour time-weighted average of 85 decibels, the department is to notify the Health and Safety Office to implement a monitoring program.

How to Conduct a Noise Risk Assessment

Noise Measurement and Monitoring

Measure workplace areas with a sound level meter (SLM) and create a noise map of facility areas. A simple example of a noise map. It can be hand-drawn in practice. After completing a noise map, identify the loudest areas on the map and the equipment in those areas. If an SLM is not available, sound measurement apps can provide a measure of area noise but may not comply with regulatory requirements.

Measure individual worker noise exposures using a personal dosimeter in areas with high noise. Use personal noise dosimeters to best assess a worker's personal noise exposure. Attach the microphone to the top of the worker's shoulder on the side that is likely to have the highest exposure. If the device does not have a separate microphone this may not be necessary.

The noise survey is performed using a sound level meter (A-scale, slow response) and/or noise dosimeter for evaluation of personal exposures. You should tell workers they are having their noise exposure monitored and provide them with an explanation of the results. Involve workers in the noise monitoring process. They can provide important information about the work environment, machinery operation, and specific job tasks. Encourage workers to tell you when changes in equipment or production occur.

Noise levels are likely hazardous if a person must raise their voice to speak with someone is an arm's length away. Measure employee noise exposures to determine if it is 85 dBA TWA8 (a-weighted decibels eight-hour time-weighted average) or higher. The employee is to be notified when he/she is exposed at or above an 8-hour time-weighted average of 85 decibels.

Do you suspect your workers are being harmed by excessive noise? Take individual decibel level measurements at discrete locations in your facility during typical operation. This important process can help answer these questions:

• What piece of machinery contributes to excessive or dangerous noise?
• Where in the plant are workers exposed to dangerous noise?
• Who is the most at risk of excessive noise exposure?

If this simple walkaround measurement indicates potential problems (levels greater than 80 dB), a more systematic plant sound survey may be needed (i.e. sound map or occupational noise survey).

Measurement Tips:

• Before measurement, calibrate your Sound Level Meter according to manufacturer’s instructions
• Use Frequency Weighting A
• Use Slow Time Weighting

To be sure of getting accurate and repeatable noise measurements that can be used for protecting workers' hearing and protecting your company from legal claims, you should use the correct grade of sound level meter. The OSHA regulations recommend the use of a Type 2 sound level meter (you can also use Type 1 as it is more accurate) with "Slow" time weighting. You should also use a Sound Level Calibrator to check that the meter is operating correctly before making important measurements.

Equivalent sound level contours. Octave band sound pressure levels may be converted to the equivalent A-weighted sound level by plotting them on this graph and noting the A-weighted sound level corresponding to the point of highest penetration into the sound level contours.

Limits for noise exposure vary across the world. Please use resources appropriate for your location when seeking out specific standards. In general, OSHA regulations set the legal limit for exposure at an average of 90 dBA over an 8 hour day. consider getting a clearer picture of the noise exposure to individual workers using Noise Dosimeters. These are small noise measurement devices worn by a worker for a typical work shift.

Time Weighted Average (TWA)

Time Weighted Average (TWA) is the average noise level during a shift (usually 8 hours).

1. Calculate the TWA.

2. The noise levels in a work place should be carefully monitored using the correct grade of equipment if there is any possibility that a worker will be exposed and an 8 hour time weighted average noise level of 85 dB(A) or above. This monitoring should be repeated periodically (e.g. every 2 years) or when there is a change in equipment, production processes or maintenance routines.

When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. If the sum of the following fractions: C1/T1 + C2/T2Cn/Tn exceeds unity, then, the mixed exposure should be considered to exceed the limit value.

This figure shows the relationship between exposure level and exposure duration under the NIOSH REL. As sounds become louder than 85 dBA, the length of a daily exposure must be reduced. For each 3 dBA increase in noise level, NIOSH recommends reducing the exposure duration by half. This is called the exchange rate. Similarly, if the daily exposure is longer than 8 hours, the allowable noise level is lower.

Hearing Protection and Controls

Eliminating or reducing harmful noise levels is the best way to protect workers. Employees are given the opportunity to select their hearing protectors from a variety of suitable hearing protectors.

When employees are subjected to sound levels exceeding 85 dBA TWA, feasible administrative or engineering controls are to be utilized. Types of administrative controls are rotation of employees, limiting time of certain operations, or restricting areas or work operations. If feasible engineering or administrative controls cannot be accomplished personal hearing protective devices must be provided and used to reduce sound levels in areas above 85 dBA. The hearing protection used will depend on the operation, employee preference and attenuation required. The safety and health officer is to assist in supplying information on attenuation data and supervise the correct use of hearing protectors.

Hearing protection, like earplugs or earmuffs, can protect you from noise if worn correctly. For employees who have experienced a standard threshold shift, hearing protectors must attenuate employee exposure to an 8-hour time-weighted average of 85 decibels or below. Signs are to be posted in areas where noise levels are above 85 dBA stating that hearing protection is required. The University strongly encourages the use of hearing protection devices while working around noisy equipment.

The employer shall evaluate hearing protector attenuation for the specific noise environments in which the protector will be used. The adequacy of hearing protector attenuation shall be re-evaluated whenever employee noise exposures increase to the extent that the hearing protectors provided may no longer provide adequate attenuation. Protection against the effects of noise exposure shall be provided when the sound levels exceed those shown in Table G-16 when measured on the A scale of a standard sound level meter at slow response.

If during any work shift a miner's noise exposure exceeds the dual hearing protection level, the mine operator must, in addition to the actions required for noise exposures that exceed the permissible exposure level, provide and ensure the concurrent use of both an ear plug and an ear muff type hearing protector. The mine operator must provide a hearing protector to a miner whose noise exposure equals or exceeds the action level under § 62.120 of this part.

When noise levels are particularly high (say > 95 dBA) you should also check that the hearing protection that you are providing is adequate. These noise exposure limits are not based on instantaneous sound levels. At no time shall any excursion exceed 115 dBA.

Hearing Tests and Audiometric Evaluation

Annual hearing tests help identify hearing loss in your employees. An audiogram is a graph of hearing thresholds at various frequencies in each ear. Thresholds which are 25 dB HL (hearing level) or better (lower) are considered normal for adults. NIOSH recommends annual audiometric testing for workers exposed to noise above the REL. Conduct testing on workers when they are first enrolled in a hearing loss prevention program. This is called baseline testing. NIOSH recommends that employers obtain baseline tests within 30 days of initial exposure for newly exposed workers.

Audiometric tests are to be pure tone, air conduction, hearing threshold examinations, with test frequencies including as a minimum 500, 1000, 2000, 3000, 4000 and 6000 Hz. The mine operator must provide audiometric tests to satisfy the requirements of this part at no cost to the miner.

Unlike baseline testing, annual hearing tests should be done as close to the end of a worker's shift as possible (no preceding quiet period). Results of annual hearing tests should be compared to results from the baseline hearing test to check for significant threshold shift (STS). NIOSH considers a 15 dB change in hearing threshold at any frequency to represent an STS. If an STS is noted during an annual hearing test, the worker should be retested within 30 days to confirm. Workers who develop an STS - whether temporary or permanent - should be notified. Steps should be taken to prevent further change in hearing.

Annual audiometric testing is performed by a licensed or certified audiologist, at UNC School of Medicine’s Speech and Hearing department. A baseline audiogram is obtained within 6 months of an employee’s first exposure at or above the action level. The baseline audiogram is established to compare against subsequent audiograms. Employees are to be notified, in writing, of the results of exams.

This audiogram shows normal hearing thresholds in the right ear. Frequency refers to how low or high the "pitch" of the sound is.

Audiometric tests shall be performed by a licensed or certified audiologist, otolaryngologist, or other physician, or by a technician who is certified by the Council of Accreditation in Occupational Hearing Conservation, or who has satisfactorily demonstrated competence in administering audiometric examinations, obtaining valid audiograms, and properly using, maintaining and checking calibration and proper functioning of the audiometers being used. A technician who operates microprocessor audiometers does not need to be certified.

Testing to establish a baseline audiogram shall be preceded by at least 14 hours without exposure to workplace noise. The mine operator must notify the miner to avoid high levels of noise for at least 14 hours immediately preceding the baseline audiogram. The mine operator must not expose the miner to workplace noise for the 14-hour quiet period before conducting the audiometric testing to determine a baseline audiogram.

Each employee's annual audiogram shall be compared to that employee's baseline audiogram to determine if the audiogram is valid and if a standard threshold shift as defined in paragraph (g)(10) of this section has occurred. The audiologist, otolaryngologist, or physician shall review problem audiograms and shall determine whether there is a need for further evaluation.

Audiometric tests shall be pure tone, air conduction, hearing threshold examinations, with test frequencies including as a minimum 500, 1000, 2000, 3000, 4000, and 6000 Hz. The functional operation of the audiometer shall be checked before each day's use by testing a person with known, stable hearing thresholds, and by listening to the audiometer's output to make sure that the output is free from distorted or unwanted sounds. Audiometer calibration shall be checked acoustically at least annually in accordance with appendix E: Acoustic Calibration of Audiometers.

Hearing Conservation Programs

Employees need to be trained on noise and hearing protection. An annual training program is provided for each employee included in the hearing conservation program. The employer shall train each employee who is exposed to noise at or above an 8-hour time weighted average of 85 decibels in accordance with the requirements of this section. The training program shall be repeated annually for each employee included in the hearing conservation program.

The employer shall administer a continuing, effective hearing conservation program, as described in paragraphs (c) through (o) of this section, whenever employee noise exposures equal or exceed an 8-hour time-weighted average sound level (TWA) of 85 decibels measured on the A scale (slow response) or, equivalently, a dose of fifty percent.

The purpose of these standards is to prevent the occurrence and reduce the progression of occupational noise-induced hearing loss among miners. This part sets forth mandatory health standards for each surface and underground metal, nonmetal, and coal mine subject to the Federal Mine Safety and Health Act of 1977.

The mine operator must, within 30 days of a miner's enrollment into a hearing conservation program, provide the miner with training. The mine operator must give training every 12 months thereafter if the miner's noise exposure continues to equal or exceed the action level.

Employee exposure measurements and assessments are maintained at the office of Environment, Health and Safety. Employee audiometric test records are kept at the University Employee Occupational Health Clinic. The OSHA noise exposure standards define two action levels at which worker protection must be provided and used. The measurements for Hearing Conservation (HC) should be made using a noise dosimeter or sound level meter with its threshold set to 80dB. The measurements for Noise Control (NC) or permissible exposure level (PEL) should be made with a threshold of 90dB.

A mine operator must provide a hearing protector to a miner whose noise exposure equals or exceeds the action level under § 62.120 of this part. The mine operator must provide audiometric tests to satisfy the requirements of this part at no cost to the miner.

Workplace Noise Risk Assessment

Conducting a workplace noise risk assessment involves a systematic approach to measure, evaluate, and control noise exposure.

1. The first step in a noise risk assessment is to identify all potential sources of noise within the workplace.
2. Conduct an initial survey to determine areas where noise levels are likely to be hazardous. Use simple tools like basic sound level meters to get an overview of the noise environment.
3. For a comprehensive assessment, detailed noise measurements are necessary.
4. Compare the measured noise levels against the relevant exposure limits and standards.
5. Determine which employees are at risk of excessive noise exposure.
6. Educate employees on the risks associated with noise exposure and the importance of using protective measures.
7. Noise levels and exposure risks should be regularly monitored and reviewed.

Performing a workplace noise risk assessment is a critical component of occupational health and safety management. By systematically identifying noise hazards, measuring exposure, evaluating risks, and implementing control measures, employers can protect their employees from the harmful effects of excessive noise.

Record Keeping and Access

Exposure measurements. Record retention. Access to records. All records required by this section shall be provided upon request to employees, former employees, representatives designated by the individual employee, and the Assistant Secretary. Transfer of records.

The authorized representatives of the Secretaries of Labor and Health and Human Services must have access to all records required under this part.